I was thinking that it would be cool if there could be a pop-up that tells you a new post was made while you are typing a long response for that thread...not those annoying ones that opens in a separate window that you have to close, but one of those java/javascript ones that kinda pop-up in a corner or side that tells you "A new post was made while you were typing"....

This way you can briefly check the new post to see if your point/question/statement was made so as to lower the likelihood of double-posting.

true, but a lot of the time i find myself typing really fast to get a good answer out there, and when i hit post, i see the page refresh and the answer was posted a few seconds before I posted mine...i guess it would just give me peace of mind when im starting a long answer and a pop-up tells me, briefly, what has just been posted so i can say..."well then....fuck this"